Conveyance servicing structure

ABSTRACT

Conveyance servicing structure includes a truck-mounted, extensible ramp arrangement in the form of a stair assembly. The stair assembly extends to various heights for servicing conveyances of various sizes or at various levels. The stair assembly includes a lower stair section, an upper stair section, and a carriage for the upper section. Extension of the stair assembly is effected by linearly extensible power means which move the carriage relative to the lower stair section, and which move the upper stair section relative to the carriage. When retracted, the upper stair section underlies the lower stair section and, when extended, the lower end portion of the upper section is contiguous to the upper end portion of the lower section to define a continuous stairway. The stair assembly can be locked in increments of one riser height, so that all the steps of the stair assembly are of uniform height.

United States Patent [72] Inventors James F. Sauer;

Leonzo V. Glidewell, both of Miami, Fla. [21] Appl. No. 55,456 [22] Filed July 16, 1970 [45] Patented Dec. 7, 1971 [73] Assignee Wollard Aircraft Equipment, line.

[54] CONVEYANCE SERVICING STRUCTURE 13 Claims, 12 Drawing Figs.

[52] US. Cl 182/63,

182/116,182/127,182/208 [51] int. Cl E06c 5/06 [50] Field of Search 182/63.

3,196,981 7/1965 Winnall 182/208 3,451,504 6/1969 Logan 182/1 FOREIGN PATENTS 842,457 7/1960 Great Britain 182/63 Primary Examiner Reinaldo P. Machado Attorney-Shanley and O'Neil ABSTRACT: Conveyance servicing structure includes a truck-mounted, extensible ramp arrangement in the form ofa stair assembly. The stair assembly extends to various heights for servicing conveyances of various sizes or at various levels. The stair assembly includes a lower stair section, an upper stair section, and a carriage for the upper section. Extension of the stair assembly is effected by linearly extensible power means which move the carriage relative to the lower stair section, and which move the upper stair section relative to the carriage. When retracted, the upper stair section underlies the lower stair section and, when extended, the lower end portion of the upper section is contiguous to the upper end portion of the lower section to define a continuous stairway. The stair assembly can be locked in increments of one riser height, so that all the steps of the stair assembly are of uniform height.

2. ll I PAIENTED nEc nan 3525306 sum 1 or 6 INVENTORS JAIIES F. SAUER LEONZO V. GLIDEWELL ATTORNEYS Mir v PATENTED DEC 7 I97! SHEET 5 0F 6 CONVEYANCE SERVICING STRUCTURE BACKGROUND OF THE INVENTION This invention relates to conveyance servicing structures. In its more particular aspects, the invention pertains to mobile apparatus for servicing aircraft at air terminal facilities.

Doorways and other areas of aircraft to be serviced by ground crews are usually located at distances far above ground level. For loading of passengers or cargo, or otherwise servicing aircraft, access to such elevated locations has often been obtained with the aid of mobile structures which are moved to the location of the parked aircraft and into position to register with the aircraft doorway or other part of the aircraft to be serviced. For example, for enplaning or deplaning passengers, mobile stairways have often been wheeled into position in registration with the aircraft doorway for the passengers to enter or exit the aircraft from or to ground level.

As the vertical distances to be traversed from ground to the part of the aircraft to be serviced become larger as a result of increases in aircraft size, the equipment necessary to traverse these distances necessarily becomes larger in order to span the long distances involved. Such equipment must have capability for servicing aircraft at various levels above ground, because the height of aircraft doorways and other parts to be serviced varies among aircraft, and of course not all of the parts of a single aircraft are at a single elevation. This requirement suggests that the servicing equipment should have the quality of extensibility, and extensible servicing structures have been proposed in the prior art. However, the extensible structures proposed heretofore have had some disadvantage or deficiency which has prevented their being satisfactory for spanning the long distances involved in servicing the new aircraft. Equipment for servicing such aircraft, while it must have high strength and be capable of spanning long distances, should be light in weight so as to be easy to transport and should not be complex because of the difficulties in mechanical construction and maintenance involved with complex structures. Further, the apparatus should provide a maximum order of safety for persons using the equipment. Accordingly, main objects of the invention are the provision of improved, extensible, conveyance servicing structures which are high in strength and capable of spanning long distances, but are lightweight, simple in construction, and safe in operation.

Other objects of the invention will appear from the following detailed description which, in connection with the accompanying schematic drawings, discloses a preferred embodiment of the invention for purposes of illustration only and not for definition of the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view of a conveyance servicing structure embodying principles of the invention.

FIG. 2 is a plan view of the structure of FIG. 1.

FIG. 3 is an enlarged view of stabilizer details of the structure of FIG. 1.

FIG. 4 is an exploded view showing the coaction of major components of the stair assembly of the structure of FIG. 1.

FIG. 5 is a side view of the stair assembly of the structure of FIG. I.

FIG. 6 is a cross-sectional view on line 66 of FIG. 5.

FIG. 7 is a view on cross section line 7-7 of FIG. 5.

FIG. 8 is a cross-sectional view on line 8-8 of FIG. 5.

FIG. 9 is a view on cross section line 99 of FIG. 5.

FIG. 10 is a top view showing details of the carriage of the structure of FIG. 1.

FIG. 11 is a cross-sectional view on line II 11 of FIG. 10.

FIG. 12 is a view on cross section line l2l2 of FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT General Arrangement FIGS. l and 2 depict a conveyance-servicing structure 30 in the form of apparatus for passengers to board or disembark from an aircraft 32. The structure includes a mobile base in the form of truck 34, an extensible ramp arrangement in the form of a stair assembly including a plurality of stair sections 36, 38 which define a continuous stairway, and a conveyanceservicing platform 40 which defines a path for passenger traftie between the aircraft and the top of the stairway.

The stair assembly forms an elevator structure for raising and lowering platform 40. Lower stair section 36 is fixedly mounted on the truck chassis, and upper stair section 38 is mounted for movement relative to the lower stair section to extend the stairway to the level of the door of the aircraft to be serviced. Aircraft vary in size and their doorways vary in height above ground, so the amount of extension of the upper stair section varies with the particular aircraft being serviced.

Upper stair section 38 carries conveyance servicing platform 40, and as the upper stair section is moved relative to the lower stair section to elongate or shorten the stairway, the platform is thereby raised or lowered to different elevations. Conveyance servicing structures generally which include the platform per se embody an invention which is claimed in copending application Ser. No. 56,288, filed July 20, I97 I, by James W. Smith, Benjamin E. Evans, William M. Riggles, and Urmas Schormann, and entitled Conveyance Servicing Structure." The details of the platform of that invention are of no interest here and would unduly burden the instant application. For purposes of understanding the instant invention, it is sufficient to know that the platform can be extended or retracted in a direction along the traffic path, that it can be moved bodily relative to support structure 2 (which fonns a part of upper stair section 38) in a direction which is lateral to the traffic path, that it can be tilted upwardly and downwardly relative to support structure 92, and that a bumper I10 (FIG. 2) on the free end of the platform can swing in a direction which is lateral to the path of traffic. The various movement features of the platforms facilitate precise registration of the platform with the part of the aircraft to be serviced. With such features, there is no need for performance of the difiicult and time-consuming task of positioning the truck on the ground with the pinpoint accuracy required to precisely register the platform with the part of the aircraft to be serviced. With the movement features of the platform, the truck can be positioned in a general area for servicing the aircraft, and precise registration of the platform can be effected by the movement features of the platform.

Base

Truck 34 has the usual chassis in the form of a framework of beams including a beam 44 at each side of the truck. Wheels 46 mount the truck for movement across the ground, and a cab 48 is provided for the vehicle operator.

The base includes stabilizers which steady the structure during loading and unloading, and control swaying in high winds. The stabilizers include a pair of forward or main stabilizers 50 which extend outboard of the truck from behind operator's cab 48. A pair of auxiliary or rear stabilizers 52 are provided at the rear of truck 34.

Each main stabilizer 50 is mounted on an upstanding beam 54 (FIG. 3) which is fixed to another beam 55 mounted on the truck chassis. Each stabilizer 50 includes a tubular support 56 which is pivotally mounted on beam 54 by a pin 58 carried between lugs on the beam. Another tubular support 60 telescopically receives upper tubular support 56. A hydraulic cylinder assembly 62 inside the tubular supports is pivotally mounted at its upper end on tubular support 56. Operating rod 64 of hydraulic cylinder assembly 62 is pivotally mounted by pin 66 on the lower end of tubular support 60. A ground-engaging pad 68 is also pivotally mounted by pin 66 on tubular support 60.

A connecting bar 70 has an outer end pivotally connected by pin 72 to tubular support 60. The inner end of connecting bar 70 is pivotally connected by pin 74 to beam 54. When operating rod 64 of hydraulic cylinder assembly 62 is retracted, tubular support 60 telescopes upwardly over tubular support 56, and the outer end of connecting bar 70 describes an arc as the stabilizer swings upwardly to a stored position illustrated in phantom lines in FIG. 3. Extension of the operating rod reverses this action swinging the stabilizer outwardly and downwardly to the operative or ground-engaging position shown in solid lines in FIG. 3.

Each rear stabilizer 52 includes a hydraulic cylinder assembly 76 having an upper end which is pivotally mounted by pin 78 on a beam 80 which is fixed to the truck chassis. Operating rod 82 of cylinder assembly 76 is pivotally mounted on a ground-engaging pad 84 by a pin 86, as is the lower end of a support arm 88 which has its upper end pivoted by pin 90 on beam 80. Retraction of operating rod 82 moves pad 84 upwardly to a stored position above the ground. Extension of rod 82 moves pad 84 downwardly into the ground-engaging position illustrated.

Platform Support Structure Conveyance servicing platform 40 (FIG. 1, 2) is mounted on support structure 92 at the upper end portion of upper stair section 38. Support structure 92 also forms a landing at the top of the stairway. Support structure 92 has an upper or walking surface defining a landing floor 94.

Support structure 92 is generally T-shaped in plan view (FIG. 2), having an outer segment 96 which is wider than the rest of the landing to provide a wide span of movement for platform 40 relative to support structure 92 in a direction which is lateral relative to the path of traffic over the platform. Platform 40 tilts, i.e., swings upwardly and downwardly about a horizontal axis which extends along the outer end portion of wide outer segment 96.

Stair Assembly With reference to FIGS. 1 and 4, the stair assembly has three major component parts or subassemblies, two of which are stair sections 36, 38. The stair sections together define a continuous path in the form of a stairway between the ground and platform 40, for passenger traffic to and from aircraft 32.

The third major component of the stair assembly is a carriage 244 for the upper stair section. The carriage, movably mounting structure for the carriage and for the upper stair section, and a hydraulic power arrangement are provided for moving upper stair section 38 relative to lower stair section 36 in a direction along the stairway to raise and lower platform 40, at the same time elongating and shortening the stairway to the required length.

Lower Stair Section Lower stair section 38 comprises a frame assembly including at each side a horizontal beam 246 (FIGS. 4, which is rigidly secured to a side beam 44 of the truck chassis. A beam 248 inclines slightly upwardly in a direction rearwardly of the vehicle and is outboard of beam 246. Beams 246, 248 are joined by crossbeam 55, and one of the upstanding beams 54 projects from crossbeam 55 at each side of the framework. A beam 254 inclines upwardly in a direction forwardly of the vehicle at each side of the lower stair frame assembly. Each beam 254 is joined to the rear end of an outboard beam 248 and to the top of an upstanding beam 54, and is fixed in position relative to the remainder of the structure of the lower stair assembly. Inclined beams 254 extend at an angle of inclination which is equal to that of the stairway.

Each of inclined beams 254 extends downwardly to a level below the respective side beam 246. Crossbeams, as 258, 260, 261 are secured to the lower end portions of inclined beams 254. A side beam 262 is joined to crossbeams 258, 260 outboard of inclined beam 254 at each side of the frame, and projects rearwardly of the vehicle. An upstanding stub beam 264 at each side of the framework supports a side stringer 266 which carries the stepping assembly of the lower stair section.

The stepping assembly includes horizontal walking portions in the form of stair treads 268 and a landing 270. The landing is located at upper end potion 272 of lower stair section 36. Vertical riser portions 274 separate walking portions which are contiguous to one another in a direction along the stairway. All of the riser portions are of equal height, and all of the tread portions are of equal width.

The walking portions and the riser portions lie in planes which intersect one another at right angles to define stair nosings 276. Since all the risers are of equal height, and since all the treads are of equal width, the stair nosings defined by intersections of the planes of the treads and risers are spaced at equal distances or intervals X" in a direction along the stairway.

Each side stringer 266 carries at its upper end portion a holddown roller bearing 278 which receives upward thrust from upper stair section 38. At each side of lower stair section 36 is a hand rail assembly 280 which is supported by a plurality of balusters 282 on side stringer 266. In practice, the balusters are covered by a skin or panelling 284 which is shown in FIG. 1 but is removed in FIG. 5 for clarity in illustration. At lower end portion 286 (FIG. 1) of the lower stair section 36 is mounted a flip-step 288 (see also FIGS. 2, 4). Flip-step 288 is pivotally mounted on side stringers 266 of stair section 36 for swinging movement about a horizontal axis defined by pivot pins joining the side stringers of the lower stair section and the sides of the flip-step. The flip-step can be rotated about from the position shown to a stored position upside down and nested between the side stringers of the lower stir section. When lowered, the flip-step affords an easy transition between the ground and the remaining steps of lower stair section 36. When lowered, the lowest tread of the flip-step is preferably above ground a distance equal to the height of one of the risers of the stair section.

Carriage Carriage 244 is mounted for movement relative to lower stair section 36 by structure including inclined beams I54 (FIGS. 5, 6) of the lower stair frame assembly, and including an arrangement of roller bearings on the carriage. These bearings are mounted on the carriage frame which includes at each side a generally H-shaped structure comprising an outer side frame member 290 and an inner side frame member 292 which are joined together by a web member 294. Frame members 290, 292, 294 at each side of the carriage define a downwardly opening recess for receiving an inclined beam 254 of the lower stair frame assembly. The inner side members 292 of the carriage frame are joined by a plurality of crossmembers 296, 298, 300 and 302 (FIGS. 10, 12). The carriage framework also includes a plurality of brace members, as 304, which strengthen the assembly.

The roller bearing arrangement includes a pair of roller bearings 306 (FIGS. 5, 6, 11) at each side of the carriage frame. The roller bearings of each pair are in opposed relation to one another, and are mounted on coaxial axles which are rotatably carried in bushings 308. One of the bushings is rigidly mounted on outer side frame member 290, and the other of the bushings is mounted on inner side frame member 292. Each of the inclined beams 254 of the lower stair frame assembly are I-section beams and have an upper flange portion 310, a lower flange portion 312, ad a web portion 314. Roller bearings 306 thrust against the underside of upper flange portions 310 of the inclined beams, and the flange portions define trackways for roller bearings 306.

The roller bearing arrangement also includes a pair of roller bearings 316 (FIGS. 5, 7, 11) at each side of the carriage frame. Each roller bearing 316 is mounted on an axle rotatably carried in a bushing 318. Bushings 318 are respectively mounted in outer and inner side frame members 290, 292 with the roller bearings of each pair in opposed relation to one another. Roller bearings 316 thrust against the upper side of lower flange portions 312 of inclined beams 254, which flange portions define trackways for the roller bearings. Roller bearings 386, 316 roll along the flange portions of the inclined beams, and thus cooperate with the beams for movement of the carriage relative to the beams.

Linearly extensible power means in the form of a hydraulic cylinder assembly 328 (FIGS. 4, 5, 12) are provided for moving carriage 244 relative to lower stair section 36. Cylinder assembly 328 has a lower end pivotally mounted by a pin 322 (see also FIG. 18) which is carried by a pair of lugs 324 fixed on crossbeam 268 and on a stub beam 326 of the lower stair section frame assembly. Stub beam 326 extends longitudinally of the vehicle between crossbeams 258, 260. Operating rod 328 (FIGS. 10, I2) of cylinder assembly 328 has an end yoke pivotally mounted on pin 338 which is carried by lug 332 on frame crossmember 388.

Hydraulic cylinder assembly 328 acts between carriage 244 and fixed mounting lugs 324 to move the carriage on roller bearings 386, 316 along inclined beams 254. Extension of operating rod 328 moves the carriage upwardly and in a direction from left to right as viewed in FIGS. 5 and 12. Retraction of the rod moves the carriage downwardly in the opposite direction.

Upper stair section 38 comprises a frame a assembly including a pair of inclined I-beams 332 (FIGS. 4, 5, 6). Beams 332 are respectively located at the opposite sides of the frame assembly of the upper stair section. The angle of inclination of beams 332 is equal to that of inclined beams 254 of the lower stair section frame assembly so beams 332 are parallel to beams 254. Side frame members 290, 292 and 294 of carriage 244 define an upwardly opening recess at each side of the carriage for receiving a beam 332.

Upper stair section 38 is mounted for movement relative to carriage 244 in a direction along the stairway by structure including inclined beams 332 and an arrangement of roller bearings on the carriage. This roller bearing arrangement includes a pair of opposed roller bearings 336 !(FIGS. 5, 8, 11) at each side of the carriage frame. Each roller bearing 336 is carried on an axle which is joumaled on a bushing 338. One of the bushings 338 of each roller pair is mounted on an outer side frame member 298 of the carriage, and the other of the bushings is mounted on an inner side frame member 292 so that the rollers are in opposed relationship. Each beam 332 includes upper and lower flange portions 337, 339 respectively, and rollers 336 engage the underside of upper flange portion 337 of the associated inclined beam 332. Rollers 336 also engage the upper side of lower flange portion 339 of the same beam. The flange portions of the beams thus define trackways for roller bearings 336.

The roller bearing arrangement of which roller bearings 336 form a part also includes a pair of roller bearings 348 (FIGS. 5, 9, III) at each side of the carriage. Each of bearings 340 is mounted on an axle joumaled in a bushing 342 and the bushings are respectively mounted in outer side frame member 298 and inner side frame member 292 so that the rollers are in opposed relation to one another. Roller bearings 348 thrust against the under side of upper flange portions 337 of beams 332, which flange portions thus define tracks for roller bearings 348.

Roller bearings 336, 348 cooperate with inclined beams 332 of upper stair section 38 for movement of the upper stair section relative to carriage 244. Centering roller bearing assemblies 344 (FIGS. 7, 9, III) are spaced along the carriage and thrust against the web portions of the inclined beams of the upper and lower stair sections. A roller bearing 345 (FIGS. 6, 18, 11) at each side of the carriage frame runs along the lower flange portion of beam 332. Roller bearings 345 are adjustable vertically as viewed in FIG. 6 to remain in contact with the lower flange portion and thereby eliminate any play which may develop in the structure.

Linearly extensive power means in the form of a hydraulic cylinder assembly 346 (FIGS. 4, 18, 12) are provided for moving upper stair section 38 relative to carriage 244. Cylinder assembly 346 includes a lower end which is pivotally mounted by a pin 348 (FIG. 12) carried between a pair of lugs 350 on carriage frame member 296. Operating rod 352 of cylinder assembly 346 is pivotally mounted by a pin 354 carried between a pair of lugs 356 which are fixed to a crossbeam 358 in the frame of upper stair section 38 (see also FIG. 5).

Hydraulic cylinder assembly 346 acts between carriage 244 and-upper stair section 38 to move upper section 38 on roller bearings 336, 238 of the carriage. Extension of operating rod 352 moves upper stair section 38 upwardly in a direction from left to right as viewed in FIGS. 5 and 12. Retraction of operating rod 352 moves the upper stair section downwardly in the opposite direction.

Upper Stair Section The frame assembly of upper stair section 38 includes inclined beams 332 and a box beam 360 (FIG. 6) mounted on each inclined beam 332. Each box beam 368 is welded to upper flange portion 337 of inclined beam 332, and inwardly projecting, elongated side frame plates 362 are secured to the top surfaces of beams 368. Holddown rollers 278 (FIG. 5) of lower stair section 36 run along side frame plates 362.

Upper stair section 38 includes lower and upper end portions 364, 368 respectively (FIGS. 1, 5). Platform support or landing structure 92 is located at upper end portion 368. A side stringer 370 (FIGS. 4, 6) forming part of the upper stair frame assembly is mounted on an inwardly projecting, side frame plate 362 at each side of the frame assembly, (FIG. 5, 6).

The upper stair section includes a plurality of horizontal walking portions in the form of stair treads 372 and floor 94 of landing structure 92. Vertical risers 374 separate contiguous walking portions. The walking portions and risers lie in planes which intersect at right angles to define stair nosings 376 like stair nosings 276 of lower stair section 38. Treads 372 and risers 374 are carried by side stringers 370.

All the risers of the upper stair section are of equal height, and all of the treads are of equal width. The height of the risers of the upper stair section is equal to the height of the risers of the lower section, and the width of the treads of the upper section is equal to the width of the treads of the lower section Accordingly, stair nosings 376 defined by intersections of the planes of the treads and risers of the upper stair section are spaced at equal intervals X in a direction along the stairway, and these intervals are equal to the intervals )I" between the nosings defined by the planes of the treads ad risers of the lower stair section.

Upper stair section 38 includes a handrail 378 at each side of the stairway. Each rail is supported by a plurality of balusters 380 which are secured to beams 332 and box beams 360. In practice, the balusters are covered by a skin or panelling 382 (FIG. 1) which is removed in FIG. 5 for clarity in illustration.

Carriage cylinder assembly 328 (FIG. 4) and upper stair section cylinder assembly 346 coact to move carriage 244 and upper stair section 38 to displace the upper stair section between a lowered position (illustrated in FIG. 5) and an extended position (illustrated in FIG. I). In the lowered position (FIG. 5) the upper stair section underlies the lower stair section, along the lower stair section, and lower end portion 364 of upper stair section 38 is on a lower level than, and is spaced in a direction along the stairway from, upper end portion 272 of lower stair section 36.

When extended (FIG. 1), upper stair section 38 is aligned relative to the lower stair section in an orientation in which lower end portion 364 of upper stair section 38 is contiguous to upper end portion 272 of lower stair section 36 so that the stair sections define a continuous stairway for passenger traffic to and from aircraft 32.

Locking Structure Upper stair section 38 can be raised from the position of FIG. to any of a number of elevated positions short of the extended position illustrated in FIG. 1, the degree of extension of the stairway being dependent on the doorway height of the particular aircraft to be serviced. Extension is affected in increments of one step, i.e., one riser height, and there is provided a locking arrangement which, whether the stairway is fully or partly extended, locks the stair sections with a distance of one riser height between walking portions of the lower and upper stair sections. Stated differently, the locking structure locks the upper stair section relative to the lower stair section in a position inwhich the lowest exposed walking portion of the upper stair section (i.e., the walking portion which is closest to the landing of the lower stair section) is a distance equal to the height of one riser above the floor of the landing of the lower stair section. Which of the walking portions of the upper stair section is contiguous to the landing of the lower stair section varies with the degree of extension of the stairway.

The upper stair section is advanced and locked in increments of one full riser height, so that all of the steps from the lower end of the lower stair section to the upper end of the upper stair section are of equal height irrespective of the amount of extension of the stairway. As will be developed, the incremental locking feature of the stair assembly has special coaction with the tilting features of the platform, which makes it possible to obtain a uniform step height all along the stairway yet provide a servicing platform at the exact level of any aircraft doorsill.

The locking structure includes a catch arrangement including a plurality of pawls, and a catch-holding arrangement in the form of a plurality of detents, and the pawls and detents cooperate to lock the stair sections in position. The pawl arrangement includes a carriage-locking pawl 384 (FIG. 5, 7, 11) at each side of the carriage. PawI 384 is pivotally mounted on a bushing which is coaxial with the axle of the roller bearing 316 which is mounted in inner side frame member 292 of the carriage. Notches are formed in a rack 368 which is welded to lower flange portion 312 (FIG. 7) of each of inclined beams 254 of the lower stair section frame assembly. The detents for cooperation with carriage-locking pawls 384 take the form of a plurality of catch-retaining surfaces 388 (FIG. 11) in the notches. Detents 388 are spaced in a direction along the stairway at equal intervals X which are equal to the intervals X" between the stair nosings defined by the intersections of the planes of the treads and risers of the upper and lower stair sections.

The locking structure includes an actuating mechanism which comprises at each side of the carriage a link 390 having one end which is pivotally mounted on pawl 384 eccentrically of the axis of pivoting of the pawl. The opposite end of link 390 is pivotally connected to the lower end of another link 392 which has an upper end rigidly secured to a shaft 394 (see also FIGS. 9, 12). A return spring 396 (FIG. 11) has one end secured to an intermediate portion of link 392, and an opposite end secured to inner side frame member 292 of carriage 244.

Shaft 394 spans the carriage width (FIG. 9) and is rotatably mounted in bearings carried in bearing mounts 398 (FIGS. 10, 11) which are secured to the inner side frame members at the opposite sides of the carriage. Between bearing mounts 398, a curved arm 400 (FIGS. 9, 10, 12) has its lower end rigidly secured to shaft 394. The upper end of arm 400 is pivotally connected to a pin extending between the ears of a yoke forming a portion of a plunger 402 of a solenoid 404 which is attached to crossmember 302 of the carriage frame. Through shaft 394, solenoid 404 actuates the pawl 384 at each side of the carriage.

Each carriage-locking pawl 384 is mounted on the carriage for movement between a first or locking position (illustrated in FIG. 11) in which pawl 384 operatively engages a detent 388 in rack 386 to lock the carriage against downward movement relative to the lower stair section, and a second or inoperative position in which the pawl is out of operative engagement with the detent and the carriage is free to move downwardly relative to the lower stair section. Movement of the pawl from one position to the other is effected by the actuating mechanism as follows: Energization of solenoid 404 (FIG. 12) retracts plunger 202, thereby swinging arm 400 in a counterclockwise direction as viewed in the drawings, and thus rotating shaft 394 counterclockwise. Such rotation of shaft 394 swings each arm 392 (FIG. 11) counterclockwise against the tension of spring 396. Swinging of arm 392 moves link 390 to the right, swinging pawl 384 clockwise about the axis of bearing 316 so that the detent-engaging lower tip of the pawl swings above rack 386. As will be developed, the carriage is slightly raised (i.e., moved from left to right) relative to the lower stair section from the position illustrated before unlocking, so that the lower tip of the pawl can clear the upper edge of detent 388 and swing clockwise to unlocked position.

When solenoid 404 is deenergized, spring 396 rotates arm 392 clockwise, thereby moving link 390 to the left. This rotates pawl 384 counterclockwise, swinging its detent-engaging tip downwardly into contact with the top surfaces of rack 386. As will be more fully described, if the tip of the pawl is not at a detent, the carriage is moved downwardly along the rack (i.e., from right to left as viewed in FIG. 11) until a detent 388 is engaged by the pawl. The detents are positioned, and spaced at intervals X" as noted above, so that whenever the pawl engages a detent, one of the walking portions of upper stair section 38 is at an increment of one riser height above the floor of the landing of the lower stair section. Unless, of course, the stairway is fully lowered, when the landing floor of the upper stair section is coplanar with the floor of the landing of the lower stair section, as shown in FIG. 5. FIG. [1 depicts the relative positions of the parts at one detent short of full extension of the carriage relative to the lower stair section. When the pawl engages the leftmost detent, the carriage is locked in the fully lowered position of FIG. 5.

A stop block 406 is bolted to the underside of web 294 of the carriage side frame structure at each side of the carriage. Each block 406 has a downwardly facing, inclined surface which is complementary with an upwardly facing, inclined surface on another stop block 408 which is bolted to the side of carriage 292. The stop blocks coact for added rigidity of the locking structure, and provide a fail-safe mechanism to prevent the carriage from overriding the pawl.

The pawls of the locking structure also include, at each side of the carriage, an upper stair-locking pawl 410 (FIGS. 5, 9, 11). Each pawl 410 is pivotally mounted on a bushing which is coaxial with the axle of the roller bearing 340 mounted on inner side frame member 292 of the carriage. Notches are formed in an upper rack 412, one of which is welded to each of box beams 360 (FIG. 9) of the upper stair frame assembly. Detents in the form of pawl-retaining surfaces 414 (FIG. 11) in the notches are spaced along the stairway at equal intervals X which are equal to the intervals X between the stair nosings defined by the planes of the treads and risers of the upper and lower stair sections.

The actuating mechanism for each pawl 410 includes a link 416 which has one end pivotally mounted on pawl 410 eccentn'cally of the axis of swing of the pawl. The opposite end of link 416 is pivotally mounted on the upper end of an arm 418 which has a lower end rigidly secured to a shaft 420 (see also FIGS. 9, 10, 12). Shaft 420 is parallel to shaft 394, and is rotatably carried in bushings in bearing mounts 398.

Between the bearing mounts an arm 422 (FIGS. 9, 10) has a lower end rigidly secured to shaft 420. The upper end of arm 422 is pivotally mounted on a pin carried between the ears of a yoke (FIG. 10) of a plunger 424 of a solenoid 426 which is secured to crossmember 302 of the carriage frame. Through shaft 420, solenoid 426 actuates the pawl 410 at each side of the carriage.

Each pawl 418 is mounted on the carriage for movement between a first or locking position (illustrated in FIG. 11) in which pawl 410 operatively engages a detent 414 of rack 412 to lock upper stair section 38 against downward movement relative to carriage 244, and a second or inoperative position in which pawl 410 is down out of operative engagement with the detent and the upper stair section is free to move downwardly relative to the carriage. Movement of pawl 418 from locking to inoperative position is effected by the actuator as follows: Energization of solenoid 426 (FIG. 10) retracts plunger 424 thereby swinging arm 422 and rotating shaft 420 (FIG. llll) counterclockwise. Rotation of shaft 420 swings arm 418 counterclockwise, thereby moving link 4116 to the left and thus swinging pawl 410 clockwise about its axis so that the upper, detent-engaging tip of pawl 410 swings downwardly below the detents in rack 412. As will be described, upper stair section 38 is moved slightly upwardly (i.e., from left to right in FIG. 11) relative to the carriage from the position illustrated, to provide clearance for pawl 410 to move to inoperative position.

When solenoid 426 is deenergized, gravity acts on the lower left end portion of the pawl to swing the pawl counterclockwise so that the upper, detent-engaging tip of pawl 410 swings upwardly into contact with the bottom surfaces of rack 4112. If the tip of the pawl is not at a detent, the upper stair section is moved downwardly (i.e., from right to left) and the tip of the pawl rides the bottom surfaces of rack 412 until it engages a detent 414. As with lower rack 386, the detents in the upper rack 412 are positioned, and spaced at intervals X," so that whenever pawl 418 engages a detent 414 one of the walking portions of the upper stair section is at an increment of one riser height above the landing of the lower section (unless the stairway is in the fully retracted positions of FIG. 5). In FIG. II, the parts are shown with the upper stair section fully retracted relative to the carriage. At full extension, pawls 410' engage the leftmost detents 4B4.

A stop block 428 is bolted to the top side of web frame member 294 at each side of the carriage. Block 428 has an inclined, upwardly facing surface which is complementary to an inclined, downwardly facing surface of another stop block 438 which is bolted to the side of carriage 292. These stop blocks coact for rigidity in the locking structure, and aid in preventing the mass of the upper stair section from causing it to override pawls 410.

Barriers With reference to FIGS. I and 2, handrail structure at the top of the stairway includes two barrier sections 432, 434 at each side of the stairway. Barrier section 432 is hingedly mounted on support structure 92 so that barrier section 432 can swing in a direction which is lateral relative to the path of trafiic. Barrier section 434 has a forward end portion which is mounted on platform 40 for swinging movement laterally relative to the traffic path. Barrier sections 432 and 434 are hingedly interconnected for swinging movement relative to one another and laterally relative to the traffic path. With this arrangement, as best visualized from FIG. 2, the barrier sections swing and fold as platform 40 moves sidewise, and guard the sides of the traffic path irrespective of the position of lateral displacement of the platform. Barrier section 434 is also hingedly connected to platform 40 for relative movement about a horizontal axis, so that the platform can swing relative to support structure 92 in an upward and downward direction without interference from barrier 434.

Platform 40 at each side also carries a forward barrier section 448 which includes an extensible portion 452 which telescopically extends and retracts to correspond with the extension and retraction of platform 48.

Operation In a preferred mode of operation, conveyance servicing structure 30 (FIG. I) is held in a storage area with stabilizers 50, 52 retracted, flip-step 288 in nested position, and upper stair section 38 and carriage 244 in the fully retracted positions if FIG. 5. To service an aircraft, truck 34 (FIG. ll) is driven to the location of the aircraft and oriented in a position for registering the platform with the aircraft doorway. The truck is parked in this position, stabilizers 50 and 52 (FIG. 3) are lowered, and the structure is ready for extension of the stairway. Controls for these operations are housed in the cab of the truck.

The operating rod of carriage cylinder assembly 320 (FIGS. 4, 5, 12) is then extended to raise carriage 244 relative to lower stair section 36. Each of the pawls 384 (FIG. Ill) can be allowed to ride the upper surfaces of rack 386 as the carriage moves to the right relative to the rack or, after the carriage has been raised slightly, solenoid 404 (FIG. 12) can be energized to move link 390 (FIG. III) to the right to swing and hold pawls 384 up out of engagement with racks 386. In either event, upper stair section 38 remains locked to carriage 244 as the carriage moves upwardly, carrying the upper stair section.

When carriage 244 has been extended as far as desired, extension of the operating rod of carriage cylinder assembly 320 (FIG. 12) is ceased and solenoid 404, if in the energized state, is deenergized. Spring 396 (FIG. 11) rotates each pawl 384 into contact with the upper surfaces of the respective rack 386 and, if the pawl is not at a detent, the carriage is moved downwardly with the lower tip of pawl 384 riding the upper surfaces of the rack until the tip of the pawl engages a detent 388. At this time, the lowest exposed step of the upper stair section is one riser height above the floor of landing 270 (FIGS. ll, 5) of the lower stair section. The stair structure can be used in any risenheight incremental extension of the carriage relative the lower stair section of emplaning and deplaning passengers.

However, assuming that not even full extension of the carriage is sufficient to attain the height of the aircraft to be serviced, extension of the operating rod of upper stair cylinder assembly 346 (FIGS. 4, 12) is then initiated, thereby moving upper stair section 38 upwardly relative to the stationary, locked carriage. The long distance of travel of the upper stair section from the retracted position of FIG. 5 to the fully extended position of FIG. 1 is thus divided between the hydraulic cylinder assemblies 320 and 326, so that neither power means need be inordinately long. For upward movement of upper stair section 38 relative to carriage 244, each of the stair-locking pawls 410 (FIG. 11) can be allowed to ride the under surfaces of the respective rack 412 as the upper stair section 38 moves to the right relative to the carriage. However, solenoid 426 (FIG. 10), can be actuated if desired (after the upper stair section has been slightly raised relative to the carriage) to swing and hold pawls 410 (FIG. 11) down out of engagement with racks 412.

When upper stair section 38 has been extended to bring the platform as closely as possible to coplanar relationship with the aircraft doorsill, extension of the operating rod of stair cylinder assembly 346 is terminated and solenoid 426 (FIG. 10), if energized, is returned to deenergized condition. Each pawl 410 (FIG. 1 I) swings up into engagement with the lower surfaces of a rack 412 and if the pawl is not at a detent, the upper stair section is moved downwardly (from right to left as viewed in FIG. 11) until the tip of pawl 410 engages a detent 414. When this occurs, the lowest exposed step of the upper stair section is one riser height above the floor of landing 270 (FIGS. 1, 5) of the lower stair section and all of the steps of the stairway are of uniform height.

The operator then leaves the cab of the truck, moves to the rear of the vehicle, and swings flip-step 288 (FIGS. ll, 4) downwardly from its stored position to the position illustrated. The operator then climbs the stairway to landing structure 92 at the top of the upper stair section where are located the controls for platform 40. The operator manipulates the platform controls to extend the platform, move it bodily sidewise, and/or tilt it upwardly or downwardly as necessary to bring the platform into precise registration with the aircraft doorway.

When the platform is extended to engage the aircraft, bumper IIO automatically swings laterally to accommodate any nonperpendicularity of the platform relative to the aircraft. As pointed out in the above-mentioned copending patent application, the tilting feature of the platfonn is particularly advantageous in combination with a riser-height incremental stair locking feature in passenger boarding stairs because with such combination it is possible to index the platform precisely coplanar with an aircraft door sill even though the sill is not at an even multiple of the riser height above ground.

When servicing the aircraft is completed, platform 40 is retracted from the aircraft. The operator descends the stairway, swings up flip-step 288, and reenters the cab of the truck.

The operating rod of stair cylinder assembly 346 (FIG. 12) is then slightly extended to raise upper stair section 38 a very slight distance relative to the carriage, just sufficient to allow unlocking of pawls 410 (FIG. 11). Solenoid 426 (FIG. is then energized to unlock pawls 410 (FIG. 11) and hold them downwardly out of engagement with racks 412. The operating rod of the stair cylinder assembly is then retracted, lowering upper stair section 38 downwardly along the carriage. Upon full retraction of the upper stair section relative to the carriage, the solenoid is deenergized and each pawl 410 swings upwardly and catches on the highest detent 414 of the associated rack 412.

The operating rod of carriage cylinder assembly 320 (FIG. 12) is then extended very slightly, to raise the carriage a distance just sufi'icient to permit unlocking of pawls 384 (FIG. 11). Solenoid 404 (FIG. 12) is then energized to swing each pawl 384 (FIG. 1 I upwardly and hold the pawl out of engagement with the respective rack 386. The operating rod of the carriage cylinder assembly is then retracted, lowering the carriage and the upper stair section relative to lower stair section 36. When fully lowered the solenoid is deenergized and each pawl 384 swings downwardly and catches on the lowest detent 388 in the associated rack 386. Stabilizers 50, 52, (FIG. 3) are then raised, and the truck is returned to its storage area.

General Discussion Apparatus built in accordance with principles of the invention are highly advantageous. The conveyance servicing structures have high strength and are capable of spanning long distances from ground to the various parts of very large aircraft. Yet, the structures are light in weight and simple in construction. The long travel distance of the upper stair section is advantageously divided between two hydraulic cylinder assemblies so that there is no need for complicated, extra-long linearly extensible power means.

The stair assembly is highly safe in operation. A major contribution to safety is made by the structure whereby the stairs are locked at increments of one riser height so that all the steps of the stair assembly are at a uniform riser height for maximum sureness of footing by persons using the stairway.

In the narrative of the foregoing detailed description, a preferred embodiment of the invention has been described. Many other embodiments are possible. For example, the walking portions for passenger or service personnel traffic can be replaced by moving conveyor belts for loading and unloading baggage or other cargo traffic. The linearly extensible power means which move the carriage and the upper stair section can be Sagamore screwjacks, or racks and pinions, instead of the hydraulic cylinder assembles illustrated. Or, principles of the invention can be adapted to structures for mechanical servicing of aircraft engines and other parts. These and many, many other modifications can be made without departing from the principals of the invention, for definition of which reference will be made to the appended claims.

We claim:

I. Conveyance servicing structure, comprising a base,

a first ramp section carried by the base and having opposite first and second end portions,

a carriage carried by the base,

a second ramp section mounted on the carriage and having opposite first and second end portions,

means mounting the carriage for movement relative to the first ramp section,

means mounting the second ramp section for movement relative to the carriage, and

motive means for moving the carriage and second ramp section to displace the second ramp section between a first position in which the second ramp section lies along the first ramp section and the first end portion of the second ramp section is spaced from the second end portion of the first ramp section, and

a second position in which the second ramp section is aligned with the first ramp section with the first end portion of the second ramp section contiguous to the second end portion of the first ramp section to define a continuous path for traffic to and from a conveyance.

2. The structure of claim I, the motive means including first linearly extensible power means acting between the carriage and a location fixed in position relative to the first ramp section for moving the carriage relative to the first ramp section, and

second linearly extensible power means acting between the carriage and the second ramp section for moving the second ramp section relative to the carriage.

3. The structure of claim I,

wherein each of the first and second ramp sections comprises a stair section having walking portions and riser portions,

wherein the riser portions of the stair sections are of substantially equal height, and including means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the first and second ramp sections.

4. Conveyance servicing structure, comprising a base,

means mounting the base for ground-traversing movement,

a lower stair section carried by the base and having opposite lower and upper end portions,

a carriage carried by the base,

an upper stair section mounted on the carriage and having opposite lower and upper end portions,

first mounting means mounting the carriage for movement relative to the lower stair section,

second mounting means mounting the upper stair section for movement relative to the carriage, and

motive means for moving the carriage and upper stair section to displace the upper stair section between a first position in which the upper stair section lies along the lower stair section and the lower end portion of the upper stair section is spaced from the upper end portion of the lower stair section, and

a second position in which the upper stair section is aligned with the lower stair section with the lower end portion of the upper stair section contiguous to the upper end portion of the lowest stair section to define a continuous stairway for trafiic to and from a conveyance,

the motive means including first linearly extensible power means acting between the carriage and a location fixed in position relative to the lower stair section for moving the carriage relative to the lower stair section, and

second linearly extensible power means acting between the carriage and the upper stair section for moving the upper stair section relative to the carriage.

5. The structure of claim 4,

wherein each of the lower and upper stair sections has walking portions and riser portions,

wherein the riser portions of the stair sections are of substantially equal height, and including lock means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the lower and upper stair sections.

6. The structure of claim 5,

the walking portions including tread portions of substantially equal width,

the tread portions and riser portions lying in planes which intersect to define stair nosings which are spaced at substantially equal intervals in a direction along the stairway,

the lock means including cooperating catch means and catch-holding means,

the catch-holding means being spaced in a direction along the stair sections at intervals which correspond to the intervals between the stair nosings.

7. The structure of claim 6,

the first mounting means including at least one first beam member fixed in position relative to the lower stair section and extending generally parallel to the stairway, and

first bearing means mounted on the carriage in cooperating relationship with each first beam member for movement of the carriage relative to the first beam member,

the second mounting means including at least one second beam member fixed in position relative to the upper stair section and extending generally parallel to each first beam member, and

second bearing means mounted on the carriage in cooperating relationship with each second beam member for movement of the second beam member relative to the carriage,

8. The structure of claim 7,

the catch-holding means including first detent means operatively associated with at least one first beam member, and

second detent means operatively associated with at least one second beam member,

the catch means including at least one first catch member mounted on the carriage for movement between a first position in which the first catch member operatively engages a first detent means to lock the carriage against movement relative to the lower stair section, and

a second position in which the first catch member is out of operative engagement with the first detent means and the carriage is free to move relative to the lower stair section, and

at least one second catch member mounted on the carriage for movement between a first position in which the second catch member operatively engages a second detent means to lock the upper stair section against movement relative to the carriage, and

a second position in which the second catch member is out of operative engagement with the second detent means and the upper stair section is free to move relative to the carriage.

9. The structure of claim 4,

the lower stair section including a landing at the upper end portion,

the upper stair section underlying the lower stair section when the upper stair section is in the first position.

110. The structure of claim 4,

the lower stair section being fixedly positioned on the base.

llll. Conveyance servicing structure, comprising a base,

means mounting the base for ground-traversing movement,

a lower stair section carried by the base and having opposite lower and upper end portions,

a carriage carried by the base,

an upper stair section mounted on the carriage and having opposite lower and upper end portions,

first mounting means mounting the carriage for movement relative to the lower stair section,

the first mounting means including at least two first beam members fixed in position relative to the lower stair section and extending generally parallel to the stairway,

each first beam member having track portions, and

first bearing means mounting on the carriage in cooperating relationship with the track portions to move along the track portions,

second mounting means mounting the upper stair section for movement relative to the carriage,

the second mounting means including at least two second beam members fixed in position relative to the upper stair section and extending generally parallel to the first beam members,

each second beam member having track portions, and

second bearing means mounted on the carriage in cooperating relationship with the track portions of the second beam members for movement of the second beam members relative to the carriage,

the carriage including opposite side frame members including inner and outer supports and defining recesses for receiving the first and second beam members,

the first and second bearing means being mounted on the inner and outer supports of the side frame members, and

motive means for moving the carriage and upper stair section to displace the upper stair section between a first position in which the upper stair section lies along the lower stair section and the lower end portion of the upper stair section is spaced from the upper end portion of the lower stair section, and

a second position in which the upper stair section is aligned with the lower stair section with the lower end portion of the upper stair section contiguous to the upper end portion of the lower stair section to define a continuous stairway for traffic to and from a conveyance,

the motive means including first linearly extensible power means acting between the carriage and a location fixed in position relative to the lower stair section for moving the carriage along the lower stair section, and

second linearly extensible power means acting between the carriage and the upper stair section for moving the upper stair section relative to the carriage.

12. The structure of claim 1 1,

wherein each of the lower and upper stair sections has walking portions and riser portions,

wherein the riser portions of the stair sections are of substantially equal height,

wherein the walking portions include tread portions of substantially equal width,

wherein the tread portions and riser portions lie in planes which intersect to define stair nosings which are spaced at substantially equal intervals in a direction along the stairway, and including lock means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the lower and upper stair sections,

the lock means including cooperating catch means and catch-holding means,

the catch-holding means being spaced in a direction along the stair sections at intervals which are substantially equal to the intervals between the stair nosings,

the catch-holding means including first detent means operatively associated with the first beam members and second detent means operatively associated with the second beam members,

the catch means including at least one first catch member mounted on the carriage for movement between a first position in which the first catch member operatively engages a first detent to lock the carriage against movement relative to the lower stair section, and

a second position in which the first catch member is out of operative engagement with the first detent means and the carriage is free to move relative to the lower stair section, nd

at least one second catch member mounted on the carriage for movement between 13. The structure of claim 12,

the walking portions of the lower stair section including a landing at the upper end portion,

the upper stair section underlying the lower stair section when the upper stair section is in the first position.

Patent No.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION December 7, 1971 Dated Inv James F Sauer and Leonzo V. Glidewell It is certified that error appears in the aboveand that said Letters Patent are hereby corrected as Column Column Column Column Column Column 2, line 28, line 29, line 36,

4, line 35, line 46, line 69,

5, line 28,

assembly line 41,

6, line 12, line 52,

10, line 3,

line 56,

14, line 1,

line 73,

identified patent shown below:

"1971" should read 1970 1 "Benjamin" should read Benjiman "2" should read 92 "stir" should read stair "154" should read 254 "ad" should read and "frame a assembly" should read frame "336! (FIGS should read 336 (FIGS "230" should read 340 "ad" should read and "if" should read of "doorsill" should read door sill "mounting" should read mounted "nd" should read and Signed and sealed this J th day of July 1972.

(SEAL) Att est:

EDWARD M.FLETCHER, JR. Attes ting Officer ROBERT GOT'I'SCHALK Commiss oner of Patents 

1. Conveyance servicing structure, comprising a base, a first ramp section carried by the base and having opposite first and second end portions, a carriage carried by the base, a second ramp section mounted on the carriage and having opposite first and second end portions, means mounting the carriage for movement relative to the first ramp section, means mounting the second ramp section for movement relative to the carriage, and motive means for moving the carriage and second ramp section to displace the second ramp section between a first position in which the second ramp section lies along the first ramp section and the first end portion of the second ramp section is spaced from the second end portion of the first ramp section, and a second position in which the second ramp section is aligned with the first ramp section with the first end portion of the second ramp section contiguous to the second end portion of the first ramp section to define a continuous path for traffic to and from a conveyance.
 2. The structure of claim 1, the motive means including first linearly extensible power means acting between the carriage and a location fixed in position relative to the first ramp section for moving the carriage relative to the first ramp section, and second linearly extensible power means acting between the carriage and the second ramp section for moving the second ramp section relative to the carriage.
 3. The structure of claim 1, wherein each of the first and second ramp sections comprises a stair section having walking portions and riser portions, wherein the riser portions of the stair sections are of substantially equal height, and including means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the first and second ramp sections.
 4. Conveyance servicing structure, comprising a base, means mounting the base for ground-traversing movement, a lower stair section carried by the base and having opposite lower and upper end portions, a carriage carried by the base, an upper stair section mounted on the carriage and having opposite lower and upper end portions, first mounting means mounting the carriage for movement relative to the lower stair section, second mounting means mounting the upper stair section for movement relative to the carriage, and motive means for moving the carriage and upper stair section to displace the upper stair section between a first position in which the upper stair section lies along the lower stair section and the lower end portion of the upper stair section is spaced from the upper end portion of the lower stair section, and a second position in which the upper stair section is aligned with the lower stair section with the lower end portion of the upper stair section contiguous to the upper end portion of the lowest stair section to define a continuous stairway for traffic to and from a conveyance, the motive means including first linearly extensible power means acting between the carriage and a location fixed in position relative to the lower stair section for moving the carriage relative to the lower stair section, and second linearly extensible power means acting between the carriage and the upper stair section for moving the upper stair section relative to the carriage.
 5. The structure of claim 4, wherein each of the lower and upper stair sections has walking portions and riser portions, wherein the riser portions of the stair sections are of substantially equal height, and including lock means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the lower and upper stair sections.
 6. The structure of claim 5, the walking portions including tread portions of substantially equal width, the tread portions and riser portions lying in planes which intersect to define stair nosings which are spaced at substantially equal intervals in a direction along the stairway, the lock means including cooperating catch means and catch-holding means, the catch-holding means being spaced in a direction along the stair sections at intervals which correspond to the intervals between the stair nosings.
 7. The structure of claim 6, the first mounting means including at least one first beam member fixed in position relative to the lower stair section and extending generally parallel to the stairway, and first bearing means mounted on the carriage in cooperating relationship with each first beam member for movement of the carriage relative to the first beam member, the second mounting means including at least one second beam member fixed in position relative to the upper stair section and extending generally parallel to each first beam member, and second bearing means mounted on the carriage in cooperating relationship with each second beam member for movement of the second beam member relative to the carriage.
 8. The structure of claim 7, the catch-holdinG means including first detent means operatively associated with at least one first beam member, and second detent means operatively associated with at least one second beam member, the catch means including at least one first catch member mounted on the carriage for movement between a first position in which the first catch member operatively engages a first detent means to lock the carriage against movement relative to the lower stair section, and a second position in which the first catch member is out of operative engagement with the first detent means and the carriage is free to move relative to the lower stair section, and at least one second catch member mounted on the carriage for movement between a first position in which the second catch member operatively engages a second detent means to lock the upper stair section against movement relative to the carriage, and a second position in which the second catch member is out of operative engagement with the second detent means and the upper stair section is free to move relative to the carriage.
 9. The structure of claim 4, the lower stair section including a landing at the upper end portion, the upper stair section underlying the lower stair section when the upper stair section is in the first position.
 10. The structure of claim 4, the lower stair section being fixedly positioned on the base.
 11. Conveyance servicing structure, comprising a base, means mounting the base for ground-traversing movement, a lower stair section carried by the base and having opposite lower and upper end portions, a carriage carried by the base, an upper stair section mounted on the carriage and having opposite lower and upper end portions, first mounting means mounting the carriage for movement relative to the lower stair section, the first mounting means including at least two first beam members fixed in position relative to the lower stair section and extending generally parallel to the stairway, each first beam member having track portions, and first bearing means mounting on the carriage in cooperating relationship with the track portions to move along the track portions, second mounting means mounting the upper stair section for movement relative to the carriage, the second mounting means including at least two second beam members fixed in position relative to the upper stair section and extending generally parallel to the first beam members, each second beam member having track portions, and second bearing means mounted on the carriage in cooperating relationship with the track portions of the second beam members for movement of the second beam members relative to the carriage, the carriage including opposite side frame members including inner and outer supports and defining recesses for receiving the first and second beam members, the first and second bearing means being mounted on the inner and outer supports of the side frame members, and motive means for moving the carriage and upper stair section to displace the upper stair section between a first position in which the upper stair section lies along the lower stair section and the lower end portion of the upper stair section is spaced from the upper end portion of the lower stair section, and a second position in which the upper stair section is aligned with the lower stair section with the lower end portion of the upper stair section contiguous to the upper end portion of the lower stair section to define a continuous stairway for traffic to and from a conveyance, the motive means including first linearly extensible power means acting between the carriage and a location fixed in position relative to the lower stair section for moving the carriage along the lower stair section, and second linearly extensible power means acting between the carriage and the upper stair section for moving the uppEr stair section relative to the carriage.
 12. The structure of claim 11, wherein each of the lower and upper stair sections has walking portions and riser portions, wherein the riser portions of the stair sections are of substantially equal height, wherein the walking portions include tread portions of substantially equal width, wherein the tread portions and riser portions lie in planes which intersect to define stair nosings which are spaced at substantially equal intervals in a direction along the stairway, and including lock means for locking the stair sections with a distance of substantially one riser height between contiguous walking portions of the lower and upper stair sections, the lock means including cooperating catch means and catch-holding means, the catch-holding means being spaced in a direction along the stair sections at intervals which are substantially equal to the intervals between the stair nosings, the catch-holding means including first detent means operatively associated with the first beam members and second detent means operatively associated with the second beam members, the catch means including at least one first catch member mounted on the carriage for movement between a first position in which the first catch member operatively engages a first detent to lock the carriage against movement relative to the lower stair section, and a second position in which the first catch member is out of operative engagement with the first detent means and the carriage is free to move relative to the lower stair section, nd at least one second catch member mounted on the carriage for movement between a first position in which the second catch member operatively engages a second detent means to lock the upper stair section against movement relative to the carriage, and a second position in which the second catch member is out of operative engagement with the second detent means and the upper stair section is free to move relative to the carriage.
 13. The structure of claim 12, the walking portions of the lower stair section including a landing at the upper end portion, the upper stair section underlying the lower stair section when the upper stair section is in the first position. 